During hibernation, the frog respires through its:

During hibernation, a frog's metabolic rate significantly slows down, and it often buries itself in mud or under leaves. In this state, the frog primarily respires through its skin only. The skin is highly permeable and vascularized, allowing for efficient absorption of oxygen from the surrounding environment (e.g., water in mud) and release of carbon dioxide, while the lungs are largely inactive.

• Lungs only: Lungs are less efficient during hibernation due to reduced activity and often being submerged.
• Both skin and lungs: While true for active frogs, during deep hibernation, skin respiration becomes dominant and often exclusive.
• Partly lungs, partly skin: This describes normal active respiration, not the specialized mode during hibernation.